This invention relates in general to drive train systems for transferring rotational power from a source of rotational power to a rotatably driven mechanism. In particular, this invention relates to an improved driveshaft assembly for use in such a drive train system that is axially collapsible in the event of a collision to absorb energy.
Torque transmitting shafts are widely used for transferring rotational power from a source of rotational power to a rotatably driven mechanism. For example, in most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical vehicular drive train system includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of misalignment between the rotational axes of these three shafts.
A recent trend in the development of passenger, sport utility, pickup truck, and other vehicles has been to design the various components of the vehicle in such a manner as to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle. As a part of this trend, it is known to design the drive train systems of vehicles so as to be axially collapsible so as to absorb energy during a collision. To accomplish this, the driveshaft tube may be formed as an assembly of first and second driveshaft sections that are connected together for concurrent rotational movement during normal operation, yet which are capable of moving axially relative to one another when a relatively large axially compressive force is applied thereto, such as can occur during a collision. A variety of such axially collapsible driveshaft assemblies are known in the art.
It has been found to be desirable to design axially collapsible driveshaft assemblies of this general type such that a predetermined amount of force is required to initiate the relative axial movement between the two driveshaft sections. It has further been found to be desirable to design these axially collapsible driveshaft assemblies such that a predetermined amount of force (constant in some instances, varying in others) is required to maintain the relative axial movement between the two driveshaft sections. However, it has been found that the manufacture of such axially collapsible driveshaft assemblies is somewhat difficult and expensive to manufacture than convention non-collapsible driveshafts. Thus, it would be desirable to provide an improved driveshaft assembly for use in a vehicular drive train system that is axially collapsible in the event of a collision to absorb energy and that is relatively simple and inexpensive in structure.
This invention relates to a driveshaft for use in a vehicular drive train system that is axially collapsible in the event of a collision to absorb energy and that is relatively simple and inexpensive in structure. The driveshaft includes a first driveshaft tube section that is generally hollow and cylindrical in shape. The driveshaft also includes a connecting member that is generally hollow and cylindrical in shape and that axially overlaps a portion of the first driveshaft tube section. A first end portion of the connecting member is secured to the first driveshaft tube section, such as by welding, adhesive, and the like. The driveshaft further includes a second driveshaft tube section that is generally hollow and cylindrical in shape and that axially overlaps a portion of the connecting member. A second end portion of the connecting member is secured to the second driveshaft tube section, such as by welding, adhesive, and the like. During normal operation of the drive train assembly, torque is transmitted through the driveshaft by means of the securement between the first driveshaft tube section, the connecting member, and the second driveshaft tube section. However, if a relatively large axial force is applied to the end portions of the driveshaft, either or both of the end portions of the connecting member are designed to fracture, allowing relative axial movement to occur between the first driveshaft tube section and the second driveshaft tube section. This collapsing functions to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle. An annular recess may be formed in the connecting member adjacent to either or both of the end portions that are secured to the driveshaft tube sections. Such a recess can be provided to weaken that end of the connecting member to insure that the fracture occurs reliably at the same location when a predetermined axial force is applied to the end portions of the driveshaft.